Apparatus for producing helical wire coils

Abstract

Apparatus for producing a helical wire coil which can be subdivided into discrete spiral binders for use in steno pads or other types of stationery products has a driven mandrel with a cylindrical intermediate section flanked by two frustoconical sections whose larger-diameter ends are adjacent to the respective axial ends of the cylindrical section. The wire to be coiled is fed into the inlet of a helical path which is defined by guide pins distributed around the sections of the mandrel. The inlet is adjacent to one of the frustoconical sections and the wire which is fed into the inlet advances along the helical path to be coiled during travel around the one frustoconical section, thereupon around the cylindrical section and finally around the other frustoconical section. The exposed surface of the cylindrical section may be grooved. The distance between the inlet of the helical path and the cylindrical section is less than the length of the cylindrical section, as considered in the axial direction of the mandrel. The other frustoconical section ensures that the convolutions of the coil can contract subsequent to advancement beyond the cylindrical section but remain coaxial with the mandrel.

I claim: 
     
       1. Apparatus for producing a helical wire coil, particularly a coil which is to be subdivided into spiral binders, comprising a rotary mandrel having a substantially frustoconical section and a substantially cylindrical section, said frustoconical section having a larger-diameter end adjacent to and a smaller-diameter end remote from said cylindrical section; means for rotating said mandrel; stationary guide means adjacent to said mandrel and defining a helical path whose lead at least approximates the desired lead of the coil, said path extending around said sections and having an inlet in the region of said frustoconical section so that successive increments of the wire first contact said frustoconical section; and means for supplying a length of wire into said inlet so that the wire advances along said path and is convoluted first around said frustoconical section and thereupon around said cylindrical section. 
     
     
       2. The apparatus of claim 1, wherein the distance between said inlet and said cylindrical section, as considered in the axial direction of said mandrel, is less than the length of said cylindrical section. 
     
     
       3. The apparatus of claim 1, wherein the length of said frustoconical section, as considered in the axial direction of said mandrel, is less than the length of said cylindrical section. 
     
     
       4. The apparatus of claim 1, wherein said cylindrical section has an uneven external surface to thus enhance friction between the wire and the cylindrical section. 
     
     
       5. The apparatus of claim 1, wherein said cylindrical section has an external surface provided with elongated grooves extending in substantial parallelism with the axis of said mandrel. 
     
     
       6. The apparatus of claim 1, wherein said mandrel further comprises a substantially conical third section having a larger-diameter end adjacent to said cylindrical section, said cylindrical section being disposed between said frustoconical section and said third section. 
     
     
       7. The apparatus of claim 6, wherein said third section is the frustum of a cone. 
     
     
       8. The apparatus of claim 1, wherein said guide means comprises several rows of guide elements extending substantially radially of said sections. 
     
     
       9. The apparatus of claim 1, further comprising a housing for said drive means and means for rotatably journalling said mandrel in said housing in the region of said frustoconical section. 
     
     
       10. The apparatus of claim 1, wherein said guide means comprises several sets of discrete guide elements and a common holder for each of said sets.